Noninvasive imaging of nanogram quantities of DNA in agarose electrophoresis gels

Image processing techniques which separate the DNA Kerr effect and induced electrokinetic distortion contributions to electric birefringence images of agarose nucleic acid electrophoresis gels are described. Under standard electrophoresis conditions, detection limits of 10 ng of DNA per well are obtained in hydroxyethylated agarose without signal averaging or 7.5 ng with averaging of four measurements. Maintaining constant gel temperature is shown to improve the quality of the images. Monochromatic light (589 nm) is shown to give a small increase in sensitivity compared to polychromatic (650 +/- 20 nm) light.